invention relates to a silencer for deadening noise produced from a refrigerant compressor of a refrigeration system by the effect of sound wave interference.
Almost every home is generally furnished with refrigeration system such as a household refrigerator, which is in continuous operation throughout seasons. Such a household refrigerator has a problem of noise to be solved. In the refrigerator, one critical noise source is a machine compartment enclosing a compressor and piping system connected to the compressor. More specifically, from the machine compartment is emanating relatively big noise, for example, noise produced with drive of a compressor motor, noise produced with flowing of the compressed gas, and mechanical noise produced by moving members of a compression mechanism. Further, the piping system connected to the compressor produces noise due to vibration thereof. The noise emanating from the machine compartment thus accounts for a large part of noise of the refrigerator. Accordingly, control of noise from the machine compartment contributes to noise reduction in the refrigerator.
Conventionally, compressors of the low noise type such as a rotary compressor have been employed for the purpose of reducing noise emanating from the machine compartment. Further, the construction of vibration-proofing of the compressor has been improved and the configuration of the vibration in a vibration transmission path. Further, noise absorptive and insulative members have been disposed around the compressor and piping system, thereby improving an amount of noise absorbed in the machine compartment and a noise transfer loss.
However, a plurality of ventilating openings are formed in one or more of walls defining the machine compartment for ventilating the machine compartment, and the noise produced in the machine compartment is caused to leak outward through the ventilating openings. As the result of provision of the ventilating openings, the above-mentioned conventional noise-reduction methods each have a definite limit and provide with the noise reduction of 2 dB (A) at the most.
On the other hand, with advancement of applied electronics technique including sound data processing circuitry and acoustic control technique, application of a noise control wherein noise is deadened by the effect of sound wave interference has recently been taken into consideration. More specifically, in the above-mentioned noise control, sound generated by a noise source is received by a sound receiver such as a microphone disposed in a specific position and the sound receiver generates an electrical signal in accordance with the received sound. The electrical signal is then converted to a control signal by signal converting means. The control signal is supplied to a speaker so that an artificial sound of opposite phase or 180.degree. out of phase with the noise received by the microphone and having the frequencies same as those and the amplitude same as that of the received sound is produced by the speaker, so that the artificial sound interferes with the received sound, thereby deadening the sound.
However, when such a noise control is applied to the refrigeration system such as a household refrigerator, parts of a silencer such as a microphone are employed for only the purpose of deadening noise and accordingly, the added value of the silencer is not so high from the point of the production cost thereof, which is desired to be solved.